Did a New York art advisor and a Florida interior designer steal the identity of a wealthy retiree to buy multi-million-dollar works of art at Sotheby’s last year? Federal prosecutors are alleging that Joakim von Ditmar and Antonio DiMarco used a fake name to place winning bids on Mark Rothko’s Untitled for $6.4 million and Ad Reinhardt’s No. 12 for $1.2 million in the fall of 2017, the Associated Press reported.

The auction house said in a statement that it became suspicious about the buyers and alerted authorities instead of releasing the pricey works. “Following the November auction, our discussions with the purchasers raised significant suspicion and concern for the elderly client they purported to represent and we felt it was necessary to contact the FBI,” a Sotheby’s spokeswoman told artnet News. “We are pleased that the appropriate action has been taken and the victim has been protected.”

Von Ditmar, the art advisor, and DiMarco, the interior designer, allegedly swindled the 80-year-old into signing paperwork allowing them to bid on blue-chip paintings on her behalf by convincing her the papers merely granted them access to the sales room to watch the auction. She later admitted to FBI investigators that she signed the papers without reading them.

When Sotheby’s staff contacted her after the auction, the unnamed victim claimed to know nothing about the works bought in her name and said she wasn’t even a collector, according to reports.

Von Ditmar and DiMarco have been charged with wire fraud conspiracy and aggravated identity theft. Von Ditmar declined to comment on the allegations; artnet News could not reach DiMarco.

Sotheby’s had to pay the sellers $5 million to meet their contractual obligations. However, the house said it was able to recoup part of the loss by reselling the Rothko. It will also re-offer the Reinhardt.

The FBI says it has uncovered at least two other occasions when the pair tried to use the same woman’s name to buy expensive artworks, but noted that the deals collapsed when it came time to pay.

DiMarco was arrested last week on separate theft and money laundering charges involving the same elderly victim. The woman told investigators she had paid him $400,000 to decorate her home in Bal Harbor, Florida, but he failed to complete the job.